Epidemiology of late-life depression and ethnicity research study (ELLDERS) Currently, depression is a leading cause of disability in the United States and will continue to ascend in importance as the population continues to grow older over the coming decades. For older adults, national prevalence estimates of "true" depressive disorders meeting established diagnostic criteria date back to pioneer psychiatric epidemiologic work in the nineteen-eighties. Demographically, much has changed over the past twenty-years in the public health of the United States and internationally. Middle-aged "baby boomers" are now entering retirement age and Latinos, largely ignored until the turn of the millennium, are now the largest ethnic minority in the country. Additionally, new technologies have advanced our understanding and treatment of depression over the past two decades. Yet, most Americans with depression go untreated or undertreated, especially disadvantaged ethnic and racial minorities. Thoughtful work by Alexopoulos, Krishnan and others has relied on clinical observations and patient studies of to suggest late-life depression subtypes;however these subtypes have not been examined at the population level. Updated national estimates of "true" depressive disorders in older adults are needed to inform current and projected evidence-based allocations of appropriate mental health resources for an aging population. The products of this research application may offer insights for opportunities for late-life depression prevention in an aging and increasingly diverse United States population. PUBLIC HEALTH RELEVANCE: The project application (PA-07-082) titled the Epidemiology of late-life depression and ethnicity research study (ELLDERS) is a three-year study to examine the prevalence, risks, and burden of disease associated with late- life depression at the national level. Findings from the ELLDERS will provide updated estimates on the distribution of major depression and functional status of affected older adults in the United States. The products of this research application may offer insights for opportunities for late-life depression prevention in an aging and increasingly diverse United States population.